1. Field of the Invention
The present invention relates to an image-forming apparatus such as a copying machine or a printer and particularly to an image-forming apparatus improved in a mounting structure of main circuit boards for permitting an image-forming portion to execute an image-forming process, a frame structure used in the image-forming apparatus and a method for producing the frame structure.
2. Description of the Related Art
Generally, an image-forming apparatus such as a copying machine or a printer has an image-forming portion in a casing. To permit the image-forming portion to execute an image-forming process, it is necessary to mount a main circuit board mounted with main circuits such as a power supply circuit, a control circuit and an image-processing circuit.
As a mounting structure of this type main circuit board in the related art, the main circuit board has been mounted to a casing frame forming a skeleton of the casing, through a shield chassis for an EMI (Electromagnetic Interference) countermeasure (e.g., see Documents 1 to 3).
In this case, for example, a metal plate shaped like a box has been used as the shield chassis.    [Document 1]
JP-A-2002-185154    [Document 2]
JP-A-9-222843    [Document 3]
JP-A-6-317954
In this type mounting structure of the main circuit board, it is necessary to connect the shield chassis to the casing frame to thereby connect the shield chassis to the ground. If the connection between the shield chassis and the casing frame is insufficient, the ground connection of the shield chassis is spoiled to thereby bring about fear that the effect of the EMI countermeasure cannot be fulfilled satisfactorily.
In addition, because the main board having the shield chassis needs to be mounted in the internal space surrounded by the casing frame, it is necessary to provide a space and fittings for mounting the shield chassis to thereby bring about fear that this may be a barrier to reduction in size and cost of the apparatus.